Running under a kvm host does not necessarily imply the presence of
a page mapped above the main memory with the virtio information;
however, the code includes a hard coded access to that page.
Instead, check for the presence of the page and exit gracefully
before we hit an addressing exception if it does not exist.
Signed-off-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
---
drivers/s390/kvm/kvm_virtio.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c
index 47cccd5..408447c 100644
--- a/drivers/s390/kvm/kvm_virtio.c
+++ b/drivers/s390/kvm/kvm_virtio.c
@@ -418,6 +418,21 @@ static void kvm_extint_handler(struct ext_code ext_code,
}
}
+static int __init test_devices_support(void)
+{
+ int ccode = -EIO;
+
+ asm volatile(
+ "0: cli 0(%1),0\n"
+ " ipm %0\n"
+ " srl %0,28\n"
+ "1:\n"
+ EX_TABLE(0b,1b)
+ : "+d" (ccode)
+ : "a" (kvm_devices)
+ : "cc");
+ return ccode;
+}
/*
* Init function for virtio
* devices are in a single page above top of "normal" mem
@@ -443,6 +458,12 @@ static int __init kvm_devices_init(void)
}
kvm_devices = (void *) real_memory_size;
+ if (test_devices_support() < 0) {
+ vmem_remove_mapping(real_memory_size, PAGE_SIZE);
+ root_device_unregister(kvm_root);
+ /* No error. */
+ return 0;
+ }
INIT_WORK(&hotplug_work, hotplug_devices);
--
1.7.11.4
--
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